I already tested with another instance of weechat.  Here is the output (latest git).
After installing the script "test" i did a /help and got two empty lines. I also changed some weechat options, always with same result.

17:22:32     | Installierte "perl" Skripten:
17:22:32     |   (keine)
17:22:35     |
17:22:35     | Installierte "python" Skripten:
17:22:35     |   (keine)
17:22:41     |
17:22:41     | Installierte "lua" Skripten:
17:22:41     |   (keine)
17:22:48     |
17:22:48     | Installierte "tcl" Skripten:
17:22:48     |   (keine)
17:23:05     |
17:23:05     | Installierte "ruby" Skripten:
17:23:05     |   (keine)
17:23:11     | python: Lade das Skript "/home/nils/weechat-git/.weechat_blank/python/test.py"
17:23:11     | python: registriertes Skript "test", Version 0.0.1 (test me)
17:23:17     |
17:23:17     |

How to reproduce:

- load one of the scripts
- type for example: /help
- output:
22:11:54     | perl: registered script "test", Version 0.01 (do nothing...)
22:11:57     |
22:11:57     |


SCRIPT_NAME    = "test"
SCRIPT_AUTHOR  = "bla"
SCRIPT_VERSION = "0.0.1"
SCRIPT_LICENSE = "GPL3"
SCRIPT_DESC    = "test me"

import weechat


def my_modifier_cb(data, modifier, modifier_data, string):
  return ""


weechat.register(SCRIPT_NAME, SCRIPT_AUTHOR, SCRIPT_VERSION, SCRIPT_LICENSE, SCRIPT_DESC, "", "")

weechat.hook_modifier("weechat_print", "my_modifier_cb", "")



my $SCRIPT  = "test";
my $AUTHOR  = "blafasel";
my $Version = "0.01";
my $LICENCE = "GPL3";
my $DESCRIPTION   = "do nothing...";

use strict;

weechat::register( $SCRIPT, $AUTHOR, $Version, $LICENCE, $DESCRIPTION, "", "" );

sub my_modifier_cb {
my (undef, $signal, undef, $data) = @_;
return "";
}
weechat::hook_modifier("weechat_print", "my_modifier_cb", "");